Fix a bug that manifests while running the test suite of 'python-igraph':

  https://github.com/opencollab/arpack-ng/issues/401
  https://github.com/opencollab/arpack-ng/pull/414

From d885b7be4ecdc9c1496f2d6f256f6c0d34962459 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Szabolcs=20Horva=CC=81t?= <szhorvat@gmail.com>
Date: Sun, 9 Apr 2023 16:36:35 +0200
Subject: [PATCH] fix: ensure that LAPACK RNG state is propagated

 - fixes #401, #410, #411
 - restores 'inits' variable removed in ce2e69a849da1d10dad5d6d3ec4db6120b3ecf50, ensuring that the RNG state is propagated
 - reverts e0d67054f573da351f12a226f7c7cc65a690ef3d to ensure that seed is different on each parallel thread
 - updates seed initialization of parallel pdgetv0/psgetv0 so that they match that of pzgetv0/pcgetv0
---
 PARPACK/SRC/MPI/pcgetv0.f | 48 +++++++++++++++++++++++----------------
 PARPACK/SRC/MPI/pdgetv0.f | 40 ++++++++++++++++++++++++++------
 PARPACK/SRC/MPI/psgetv0.f | 43 ++++++++++++++++++++++++++---------
 PARPACK/SRC/MPI/pzgetv0.f | 48 +++++++++++++++++++++++----------------
 SRC/cgetv0.f              | 21 ++++++++++++-----
 SRC/dgetv0.f              | 21 ++++++++++++-----
 SRC/sgetv0.f              | 21 ++++++++++++-----
 SRC/zgetv0.f              | 21 ++++++++++++-----
 8 files changed, 183 insertions(+), 80 deletions(-)

diff --git a/PARPACK/SRC/MPI/pcgetv0.f b/PARPACK/SRC/MPI/pcgetv0.f
index 59e3d1658..24fe8a0f1 100644
--- a/PARPACK/SRC/MPI/pcgetv0.f
+++ b/PARPACK/SRC/MPI/pcgetv0.f
@@ -176,13 +176,13 @@ subroutine pcgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
+      logical    first, inits, orth
       integer    idist, iseed(4), iter, msglvl, jj, myid, igen
       Real
      &           rnorm0
       Complex
      &           cnorm, cnorm2
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
       Complex
      &           cnorm_buf, buf2(1)
@@ -203,6 +203,12 @@ subroutine pcgetv0
      &           ccdotc
       external   ccdotc, pscnorm2, slapy2
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
@@ -213,26 +219,30 @@ subroutine pcgetv0
 c     | random number generator           |
 c     %-----------------------------------%
 c
+      if (inits) then
 c
-c     %-----------------------------------%
-c     | Generate a seed on each processor |
-c     | using process id (myid).          |
-c     | Note: the seed must be between 1  |
-c     | and 4095.  iseed(4) must be odd.  |
-c     %-----------------------------------%
+c        %-----------------------------------%
+c        | Generate a seed on each processor |
+c        | using process id (myid).          |
+c        | Note: the seed must be between 1  |
+c        | and 4095.  iseed(4) must be odd.  |
+c        %-----------------------------------%
 c
-      call MPI_COMM_RANK(comm, myid, ierr)
-      igen = 1000 + 2*myid + 1
-      if (igen .gt. 4095) then
-         write(0,*) 'Error in p_getv0: seed exceeds 4095!'
-      end if
+         call MPI_COMM_RANK(comm, myid, ierr)
+         igen = 1000 + 2*myid + 1
+         if (igen .gt. 4095) then
+            write(0,*) 'Error in p_getv0: seed exceeds 4095!'
+         end if
+c
+         iseed(1) = igen/1000
+         igen     = mod(igen,1000)
+         iseed(2) = igen/100
+         igen     = mod(igen,100)
+         iseed(3) = igen/10
+         iseed(4) = mod(igen,10)
 c
-      iseed(1) = igen/1000
-      igen     = mod(igen,1000)
-      iseed(2) = igen/100
-      igen     = mod(igen,100)
-      iseed(3) = igen/10
-      iseed(4) = 7
+         inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
diff --git a/PARPACK/SRC/MPI/pdgetv0.f b/PARPACK/SRC/MPI/pdgetv0.f
index 0f348b820..5a1956997 100644
--- a/PARPACK/SRC/MPI/pdgetv0.f
+++ b/PARPACK/SRC/MPI/pdgetv0.f
@@ -177,11 +177,11 @@ subroutine pdgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
-      integer    idist, iseed(4), iter, msglvl, jj
+      logical    first, inits, orth
+      integer    idist, iseed(4), iter, msglvl, jj, myid, igen
       Double precision
      &           rnorm0, buf2(1)
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
       Double precision
      &           rnorm_buf
@@ -206,6 +206,12 @@ subroutine pdgetv0
 c
       intrinsic    abs, sqrt
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
@@ -216,10 +222,30 @@ subroutine pdgetv0
 c     | random number generator           |
 c     %-----------------------------------%
 c
-      iseed(1) = 1
-      iseed(2) = 3
-      iseed(3) = 5
-      iseed(4) = 7
+      if (inits) then
+c
+c        %-----------------------------------%
+c        | Generate a seed on each processor |
+c        | using process id (myid).          |
+c        | Note: the seed must be between 1  |
+c        | and 4095.  iseed(4) must be odd.  |
+c        %-----------------------------------%
+c
+         call MPI_COMM_RANK(comm, myid, ierr)
+         igen = 1000 + 2*myid + 1
+         if (igen .gt. 4095) then
+            write(0,*) 'Error in p_getv0: seed exceeds 4095!'
+         end if
+c
+         iseed(1) = igen/1000
+         igen     = mod(igen,1000)
+         iseed(2) = igen/100
+         igen     = mod(igen,100)
+         iseed(3) = igen/10
+         iseed(4) = mod(igen,10)
+c
+         inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
diff --git a/PARPACK/SRC/MPI/psgetv0.f b/PARPACK/SRC/MPI/psgetv0.f
index d79a513b2..078e4fa8c 100644
--- a/PARPACK/SRC/MPI/psgetv0.f
+++ b/PARPACK/SRC/MPI/psgetv0.f
@@ -177,11 +177,11 @@ subroutine psgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
-      integer    idist, iseed(4), iter, msglvl, jj
+      logical    first, inits, orth
+      integer    idist, iseed(4), iter, msglvl, jj, myid, igen
       Real
      &           rnorm0
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
       Real
      &           rnorm_buf
@@ -206,20 +206,41 @@ subroutine psgetv0
 c
       intrinsic    abs, sqrt
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
 c
 c
-c     %-----------------------------------%
-c     | Initialize the seed of the LAPACK |
-c     | random number generator           |
-c     %-----------------------------------%
+      if (inits) then
 c
-      iseed(1) = 1
-      iseed(2) = 3
-      iseed(3) = 5
-      iseed(4) = 7
+c        %-----------------------------------%
+c        | Generate a seed on each processor |
+c        | using process id (myid).          |
+c        | Note: the seed must be between 1  |
+c        | and 4095.  iseed(4) must be odd.  |
+c        %-----------------------------------%
+c
+         call MPI_COMM_RANK(comm, myid, ierr)
+         igen = 1000 + 2*myid + 1
+         if (igen .gt. 4095) then
+            write(0,*) 'Error in p_getv0: seed exceeds 4095!'
+         end if
+c
+         iseed(1) = igen/1000
+         igen     = mod(igen,1000)
+         iseed(2) = igen/100
+         igen     = mod(igen,100)
+         iseed(3) = igen/10
+         iseed(4) = mod(igen,10)
+c
+         inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
diff --git a/PARPACK/SRC/MPI/pzgetv0.f b/PARPACK/SRC/MPI/pzgetv0.f
index 731fb319f..94fb705f3 100644
--- a/PARPACK/SRC/MPI/pzgetv0.f
+++ b/PARPACK/SRC/MPI/pzgetv0.f
@@ -176,13 +176,13 @@ subroutine pzgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
+      logical    first, inits, orth
       integer    idist, iseed(4), iter, msglvl, jj, myid, igen
       Double precision
      &           rnorm0
       Complex*16
      &           cnorm, cnorm2
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
       Complex*16
      &           cnorm_buf, buf2(1)
@@ -203,6 +203,12 @@ subroutine pzgetv0
      &           zzdotc
       external   zzdotc , pdznorm2 , dlapy2
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
@@ -213,26 +219,30 @@ subroutine pzgetv0
 c     | random number generator           |
 c     %-----------------------------------%
 c
+      if (inits) then
 c
-c     %-----------------------------------%
-c     | Generate a seed on each processor |
-c     | using process id (myid).          |
-c     | Note: the seed must be between 1  |
-c     | and 4095.  iseed(4) must be odd.  |
-c     %-----------------------------------%
+c        %-----------------------------------%
+c        | Generate a seed on each processor |
+c        | using process id (myid).          |
+c        | Note: the seed must be between 1  |
+c        | and 4095.  iseed(4) must be odd.  |
+c        %-----------------------------------%
 c
-      call MPI_COMM_RANK(comm, myid, ierr)
-      igen = 1000 + 2*myid + 1
-      if (igen .gt. 4095) then
-         write(0,*) 'Error in p_getv0: seed exceeds 4095!'
-      end if
+         call MPI_COMM_RANK(comm, myid, ierr)
+         igen = 1000 + 2*myid + 1
+         if (igen .gt. 4095) then
+            write(0,*) 'Error in p_getv0: seed exceeds 4095!'
+         end if
+c
+         iseed(1) = igen/1000
+         igen     = mod(igen,1000)
+         iseed(2) = igen/100
+         igen     = mod(igen,100)
+         iseed(3) = igen/10
+         iseed(4) = mod(igen,10)
 c
-      iseed(1) = igen/1000
-      igen     = mod(igen,1000)
-      iseed(2) = igen/100
-      igen     = mod(igen,100)
-      iseed(3) = igen/10
-      iseed(4) = 7
+         inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
diff --git a/SRC/cgetv0.f b/SRC/cgetv0.f
index b49e66708..c231eadcb 100644
--- a/SRC/cgetv0.f
+++ b/SRC/cgetv0.f
@@ -156,13 +156,13 @@ subroutine cgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
+      logical    first, inits, orth
       integer    idist, iseed(4), iter, msglvl, jj
       Real
      &           rnorm0
       Complex
      &           cnorm
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
 c     %----------------------%
 c     | External Subroutines |
@@ -180,6 +180,12 @@ subroutine cgetv0
      &           ccdotc
       external   ccdotc, scnrm2, slapy2
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
@@ -190,10 +196,13 @@ subroutine cgetv0
 c     | random number generator           |
 c     %-----------------------------------%
 c
-      iseed(1) = 1
-      iseed(2) = 3
-      iseed(3) = 5
-      iseed(4) = 7
+      if (inits) then
+          iseed(1) = 1
+          iseed(2) = 3
+          iseed(3) = 5
+          iseed(4) = 7
+          inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
diff --git a/SRC/dgetv0.f b/SRC/dgetv0.f
index 8be4fa26d..1d6dc01bd 100644
--- a/SRC/dgetv0.f
+++ b/SRC/dgetv0.f
@@ -157,11 +157,11 @@ subroutine dgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
+      logical    first, inits, orth
       integer    idist, iseed(4), iter, msglvl, jj
       Double precision
      &           rnorm0
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
 c     %----------------------%
 c     | External Subroutines |
@@ -183,6 +183,12 @@ subroutine dgetv0
 c
       intrinsic    abs, sqrt
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
@@ -193,10 +199,13 @@ subroutine dgetv0
 c     | random number generator           |
 c     %-----------------------------------%
 c
-      iseed(1) = 1
-      iseed(2) = 3
-      iseed(3) = 5
-      iseed(4) = 7
+      if (inits) then
+          iseed(1) = 1
+          iseed(2) = 3
+          iseed(3) = 5
+          iseed(4) = 7
+          inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
diff --git a/SRC/sgetv0.f b/SRC/sgetv0.f
index 26130a014..d861b2d6d 100644
--- a/SRC/sgetv0.f
+++ b/SRC/sgetv0.f
@@ -157,11 +157,11 @@ subroutine sgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
+      logical    first, inits, orth
       integer    idist, iseed(4), iter, msglvl, jj
       Real
      &           rnorm0
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
 c     %----------------------%
 c     | External Subroutines |
@@ -183,6 +183,12 @@ subroutine sgetv0
 c
       intrinsic    abs, sqrt
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
@@ -193,10 +199,13 @@ subroutine sgetv0
 c     | random number generator           |
 c     %-----------------------------------%
 c
-      iseed(1) = 1
-      iseed(2) = 3
-      iseed(3) = 5
-      iseed(4) = 7
+      if (inits) then
+          iseed(1) = 1
+          iseed(2) = 3
+          iseed(3) = 5
+          iseed(4) = 7
+          inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
diff --git a/SRC/zgetv0.f b/SRC/zgetv0.f
index cc13c3cfb..1fbd50851 100644
--- a/SRC/zgetv0.f
+++ b/SRC/zgetv0.f
@@ -156,13 +156,13 @@ subroutine zgetv0
 c     | Local Scalars & Arrays |
 c     %------------------------%
 c
-      logical    first, orth
+      logical    first, inits, orth
       integer    idist, iseed(4), iter, msglvl, jj
       Double precision
      &           rnorm0
       Complex*16
      &           cnorm
-      save       first, iseed, iter, msglvl, orth, rnorm0
+      save       first, iseed, inits, iter, msglvl, orth, rnorm0
 c
 c     %----------------------%
 c     | External Subroutines |
@@ -180,6 +180,12 @@ subroutine zgetv0
      &           zzdotc
       external   zzdotc, dznrm2, dlapy2
 c
+c     %-----------------%
+c     | Data Statements |
+c     %-----------------%
+c
+      data       inits /.true./
+c
 c     %-----------------------%
 c     | Executable Statements |
 c     %-----------------------%
@@ -190,10 +196,13 @@ subroutine zgetv0
 c     | random number generator           |
 c     %-----------------------------------%
 c
-      iseed(1) = 1
-      iseed(2) = 3
-      iseed(3) = 5
-      iseed(4) = 7
+      if (inits) then
+          iseed(1) = 1
+          iseed(2) = 3
+          iseed(3) = 5
+          iseed(4) = 7
+          inits = .false.
+      end if
 c
       if (ido .eq.  0) then
 c
